Now that E-10 fuels are common nationwide, chances are you have experience with the damaging effects of alcohol on marine engines and outboard motors. You may even had issues with fuel related problems in other small engines such as weed-whackers, generators, and lawn mowers.
When ethanol alcohol is added to fuel the resulting mixture does not form a tight bond. The alcohol loves water more than it does gasoline and will settle out from the mixture if the amount of moisture and temperature reach a certain point. In general terms at 80°F and with about 0.5% of water, the ethanol lets go of the gasoline and grabs onto the water molecules. In cooler temperatures, the water-alcohol mixture will fall out of solution with less moisture content.
For example, during the day your E-10 gasoline could contain 0.4% water and still be combined, but when the evening temperature drops below 50°F, the gasoline cannot “hold” 0.4% moisture so the alcohol and water drop to the bottom of the tank. Inside the motor, the same thing happens; the alcohol-water mix settles in the low areas of the fuel system. That is why you may see corrosion and deposits inside the fuel injection parts or in carburetor bowls. The corrosive action of the alcohol- water mixture that settles out is stronger than the effects of ethanol alone.
So, how does one know that there is ethanol in their gasoline, or if the percentage of alcohol is greater than what is posted on the gas pump? Many articles have been written about using measuring cups or graduated cylinders to calculate the percentage of alcohol after adding a pre-determined amount of water and gasoline. Briggs & Stratton, famous for their small 4-cycle engines, makes a handy easy-to-use tool for determining if and how much ethanol is in your fuel. It consists of a glass tube with markings on it.
Just add water up to the indicated line on the tube then add a sample of your fuel until it reaches the uppermost mark. Shake the contents well and let it stand for a few moments. The water settles to the lower part of the container and any alcohol will be attracted to the water and separate from the gasoline. Graduations on the tube indicate the exact percentage of alcohol that was previously part of the gasoline mixture.
It is available from Briggs & Stratton engine dealers or from online under part number 795161. With a list price of only $7.50, this makes for an inexpensive and indispensable tool for the person who likes to maintain his or her engines.